Humidity controlling hygrometer



J 1952 J. J. STEINMETZ 2,593,727

HUMIDITY CONTROLLING HYGROMETER Filed April 29, 1946 l! /6 l 20 I I ll 33 /y' 'tI: -Z:ZZZZ Z I GOA/7770A CONTROL ,7 INVENTOR.

JflffW/J J/W/V/t/[TZ 197' 7' ORA 5 Y Patented June 3, 1952 UNITED STATES PATENT OFFICE HUMIDITY CONTROLLING HTGROMETER 7 Joseph J. Steinmetz, Merrick, N. Y.

Application April 29, 1946, Serial No. 665,714

2 Claims. (Cl. 73337) (Granted under the act of March 3, 1883, as

I amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to humidity measuring devices, and comprises a novel hygrometer. The disclosed embodiment of the invention is particularly constructed to control atmospheric humidity.

An object of this invention is to provide a direct-reading instrument for the measurement of relative humidity.

Another object of this invention is to provide an apparatus for automatic control of humidity.

Further objects and advantages of this invention, as well as its construction, arrangement and operation, will be apparent from the following description and claims in connection with the accompanying drawing, in which:

Fig. 1 is perspective of one form of the invention,

Fig. 2 is a detail of the instrument in Fig. 1, in longitudinal cross-section, and

Fig. 3 represents a schematic wiring diagram of the instrument shown in Fig. 1, when used to activate humidity control apparatus.

The instrument shown in Fig. 1, generally designated as I0, is a hygrometer comprising a pointer II, which consists of a moisture-absorbent strip I2 and a non-moisture absorbent strip I3, both strips being flexible. The strips I2 and I3 are positioned side-by-side, and are bonded together along their adjacent contacting faces 25, as seen in Fig. 2, by means of cement, rivets or other suitable means. Rivet holes I6, Fig. 2, are provided at one end of the pointer H by means of which it is secured or fastened to a support or bracket I4 which is carried by the base 26, Fig. 1. The other end I! of pointer I I is free to move. The base 26 may be provided with the side walls or frame 23, thus constituting a container for the instrument constituting hygrometer III.

Changes in conditions of atmospheric humidity will cause the pointer I I to flex, and the free end ll of the pointer will thereby move along a predetermined path. The scale I5 is positioned to extend along and adjacent to the path of the pointer end II. The scale I5 is rigid and is provided with indicia 28, preferably in terms of relative humidity, which indicate the existing condition of atmospheric humidity according to the position of the pointer end II along the scale I5.

The two strips I2 andI 3 comprising the pointer I I may be of any two materials with appreciably difierent hygroscopic properties. The strip I2 is sufficiently moisture-absorbent that it expands or contracts with change in humidity. Strip I3 is preferably completely non-moistureabsorbent. Both strips I2 and I3 are flexible and have sufficient strength for use in a pointer of this type. The moisture-absorbent material of strip I2 may be selected from hydrophilic materials such as hydrophilic cellulosic materials, hydrophilic resins, and the like, including such compounds as regenerated cellulose, cellulose esters, cellulose ethers and synthetic hydrophilic resins.

Cellulose acetate is used in the disclosed embodiment of the invention and is a moisture absorbent or hygroscopic material that expands with an increase in humidity. Metal is impervious to moisture and is non-absorbent, and therefore does not expand or contract with change in humidity. Stresses set up in strip I2 of cellulose acetate by its absorption or yielding of moisture, because it is bonded. to the metal strip I3 that is non-absorbent cause the pointer II to bend or flex so that the free end I I of pointer II moves along the scale I5.

The bracket 22 is carried by the base 26, and is secured to one end of a thermo-responsive bimetallic strip 2I of well-known structure, which bends under temperature change. The end 29 of the bimetallic strip 2I remote from the bracket 22 is free to move under fiexure of the strip in response to atmospheric temperature changes. The scale I5 is secured to the bimetallic strip 2I at the free end 29 thereof in position to project laterally away from the strip. The scale I5 is thereby moved as indicated in dotted lines along the path of pointer end II when the bimetallic strip 2| fiexes in response to temperature change, the supporting brackets 22 and 24 of the strip 2I and pointer I I respectively being accordingly positioned with reference to each on the base 26.

The scale I5 of instrument I0 is calibrated. Calibration may be accomplished by means of any suitable hygrometer, of the wet-and drybulb variety for example, and the indicia 28 are located on the scale I5 in accordance with its calibration. v

The hygrometer I0 may be used to indicate the current condition of atmospheric humidity where the hygrometer is located, or it may be used for the control of conditions of atmospheric humidity in a room, chamber or the like enclosure.

.Electrical terminal 30 is secured to the scale Q .15 at a point along its with the condition of maximum atmospheric humidity desired in the room. The pointer II is by means of relay (9.

indicia 28 corresponding In the disclosed empath'of the end l1 of pointer H, which consti tutes the tip of the metallic strip l3-asillustrated in Fig. 2, and which therefore constitutesa suitable electrical contact.

The metal strip I3 of the pointer source of electricalenergy, terminal 330i scale l5 also being in the circuit. When the circuit is closedbetwe'en the terminal 30 and contact [1, the-circuit of line 3| is closed, for example I desiccatoror other 'de-humidifying apparatus of line 3| maybe conventional, and forms no part of the present invention. Therefore the dehumidifying apparatus is not disclosed herein.

7 The hygrometer i maybe operated to control the conditions of atmospheric humidity in a chamber, and to hold the atmospheric humidity to a norm, i. e. within the limit of a maximum beyond which atmospheric humidity may be undesirable for any of a number of possible reasons.

The terminal 30 'is located alongthe scale I ll is an electrical conductor, and is connected in line with the battery l8, Fig. 3, or other suitable- Theline 3| is provided,

proaches 'a condition of relative humidity that engages the terminal 32, which is located correspondingly along the scale IS. The relay is thereby energized to change the electrical characteristics of circuit 33 in a mannerffcrfthe air moistening' apparatus of circuit 33 to operate. Moisture is thereby added to the atmosphere in the chamber, and the relative humidity of the atmosphere is raised thereby. The pointer ll flexes in the direction upwardly of scale 15 "-aiong' indicia -28 until the contact I1 moves out oi engagement with terminal 33. The addition of moisture to the atmosphere is thus discontinned Increment deflections of the pointer H for a 1 given quantum change of relative humidity are diflerent at different temperatures. These differences in increment deflection of the pointer H are slight in an atmosphere where the temper-. ature is controlled uniformly, but in atmosphere where the temperature is not uniform the readings on a rigid scale in fixed position. may deviate from accuracy to an appreciable extent. Even in a building that is heated in the winter to maintain approximately uniform temperature, excessively erroneous readings of arigid scale in fixed position may occur, particularly in the summer time when unusually high temperatures may occur more or less frequently.

By the rigid scale l5 being mounted on the bimetallic strip 2|, to be moved thereby in response to temperature changes, the indicia 28- at theindicia 28 of. the'max'im'um desired .relative humidity, or slightly below to allow for lag move the contact I! out of engagement with and away from terminal 30 in the direction down wardlyof scale [5 along the indicia 28. The relay l9 then operates to open the circuit 3i, andthe dehumidifier is thereby put out of operation.

Although the humidity-control of hygrometer H] has been described above for lowering the atmo'spheric humidity, hygrometer I0 may be constructed also to raise the atmospheric humidity. The terminal 32 is positioned along the scale 55 at or near the indicia' 28 corresponding with the lowest relative humidity desired in the atmosphere. Deflection of pointer H by atmospheric humidity. becoming reduced moves contact H to intersect and engage the terminal 32, which is in circuit with the relay 2!), the relay 2!) being in circuit with the battery It or other source of are moved to compensate .for variations of in crement deflection of the pointer H at different temperatures. ment of scale 15 is along the path of pointer end I1. This compensation of readings by moveelectrical'energy and parallel with relay 1 8. Any

suitable air conditioning apparatus, which may be conventional and is not shown because it forms no part of the present invention, is operated by line 33, which is under control of relay 20 when the circuit is'closed between terminal 32 and contact I1.

Thus, when the atmosphere within the chamber in which the hygrometer lB is located apment of scale l5 in response to temperature changes makes the readings of scale I5 more accurate over a greater range of temperatures. The humidity measurements of hygrometer ID are sufiiciently accurate for most purposes throughout the range of atmospheric temperatures that are normal and withinthe range of temperatures encountered throughout the four seasons of a year inside a building. r 7

It is to be understood that various modifications and changes may be made in this invention without departing from the spirit and, scope thereof as set forth in the appended claims.

What is claimed is:

1. An instrument comprising a base, a pointer comprising two strips of material with respectively different hygroscopic properties, the strips being positioned side-by-side and bonded to each other along their adjacent contacting faces, the pointer being secured to the base at one of its ends, the other end of the pointer being free to move by flexure of the pointer responsive to changes in conditions of atmospheric hu,

midity, a rigid scale positioned to extend along and adjacent to the path ofthe free endof the pointer, a thermo-responsive bimetallic strip, the scale being secured to one end of the bimetallic strip projecting laterally away therefrom, the other end of the bimetallic strip being secured to the base in position to hold the scale located along the path of the free end of the pointer, the end of the bimetallic strip to which the scale is attached being free to move by flexure f of the bimetallic strip'responsive to temperature changes, the scale'be'ing' calibrated according to Temperature responsive move the position of the pointer along the scale at difierent relative humidities of the atmosphere. 2. In an instrument as defined in claim 1, the material of one of the strips of the pointer comprising a hydrophilic cellulose composition, the material of the other strip of the pointer being impervious to moisture.

JOSEPH J. STEINMETZ.

REFERENCES CITED UNITED STATES PATENTS Number Number Name Date Perkett May-6, 1913 Smith Mar. '7, 1916 Curry Oct. 29, 1918 Bristol May 15, 1934 Bogoslowsky Nov. 5, 1935 Goss Aug. 18, 1936 Kahn Nov. 12, 1946 FOREIGN PATENTS Country Date Germany June 22, 1917 

